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2017/2018 waec Practical Chemistry Alternative A

By | On April 10, 2017 (6 months ago)

NOTE THAT ^ MEANS Raise to power.

Draw Your Table As Usual And

Input The Following:-

Volume of pipette=25.00cm^3

indicator used- Methyl orange colour change at end point-yellow to orange/purple

Note Use Your School End Point.
1)

Tabulate

Burette reading|Final burette reading(cm^3)|Initial burette reading (cm^3)| Volume of acid used(cm^3)|

Rough- 24.10,0.00,24.10

First- 23.80, 0.00, 23.80

Second- 23.75, 0.00, 23.70

Third- 23.75, 0.00, 23.75

Average volume of A used = 23.80 + 23.70 + 23.75cm^3/3

=23.75cm^3
1bi)

CAVA/CcVc=2/1

Cc=CAVA/2VC

=0.100*23.75Moldm^-3/2*25.00

=0.0475moldm^-3

amount of A used = 0.100x VA/1000=0.100*23.75/1000 =0.00237

2moles Of A = 1mole of C

0.002375mol of A = 0.002375mol/2

100cm^3 of C contain 0.00237*100mol/2*25 =0
1000cm3ofCcontained0.002375x1000mol

2×25

=0.0475mol

concentration of C in moldm-3 =0.0475moldm-3
1bii)

Molar mass of Bing mol-1:

Molar mass of Na2CO3.yH2O=mass concentration of Bingdm-3

molar concentration of Binmoldm-3

=13.6gdm-3

0.0475moldm-3

=286gmol-1
1biii)

Molar mass of Na2CO3 =[(2×23)+12+(16×3)]=106gmol-1

Mass of anhydrous Na2CO3=106×0.0475gdm-3

=5.035gdm-3

Mass of water=13.6-5.035gdm-3

=8.565gdm-3

Mass of Na2CO3 =Molar mass of Na2CO3

Mass of water y×Molar mass of water

5.035=106

8.565 18y

y =106×8.565

5.035×18

=10

==================================

2a)

Tabulate

Test

(i)Fn + H2O, then filter
Observation

White residue and blue filtrate was observed
Inference

Fn is a mixture of soluble and insoluble salts
Test

(ii)Filtrate + NaOH(aq) in drops, then in excess
Observation

A blue gelatinous precipitate which is insoluble in excess NaOH(aq) was formed
Inference

Cu2 + present
Test

(iii)Filtrate + NH3(aq) in drops, then in excess
Observation

A pale blue gelatinous precipitate was formed. The precipitate dissolves or is soluble in excess NH3(aq) to give a deep blue solution
Inference

Cu2+ confirmed
Test

(iv)Filtrate + dil.HNO3 +AgNO3(aq)
Observation

No visible reaction White precipitate formed
Inference

Cl- present
Test

+NH3(aq) in excess
Observation

Precipitate dissolved in excess NH3(aq)
Inference

Cl- confirmed
2bi)First portion of residue +NaOH(aq) in drops, then in excess
Observation

White powdery precipitate which is insoluble in excess NaOH(aq)
Inference

Ca2+ present
Test

2bii)Second portion of residue + dil.HCl
Observation

Effervescence/bubbles; colourless, odourless gas evolved.

Gas turns lime water milky and turns damp blue litmus paper red.
Inference

Gas is CO2

CO3^2- or HCO3- present
====================

3i) Lime juice is cacitic in nature and the color of methyl orange in active medium is Red
3ii) Iron

(iii)chloride will be reduced to iron

(ii) with the yellow deposit of Sulphur
3iv)Addition of ethanoic acid to k2lo3 results to the liberation of a colourless or odourless gas co2 Which turns lime water milky
 
====COMPLETED====

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2 Responses

  1. Tanx alot

    by Anonymous on Apr 11, 2017 at 12:59 pm Reply

  2. ANAS ISHAQ

    by ANAS ISHAQ on Apr 12, 2017 at 12:00 pm Reply

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